Electronic Order Book (EOB)
The Formal Definition
A high-speed, software-driven matching engine operated by exchanges and ATS platforms that continuously records, matches, and displays limit orders across structured price tiers based on deterministic price-time priority.
Book Priority Hierarchy = Primary: Price Level ➔ Secondary: Display Visibility ➔ Tertiary: Order Entry Timestamp
Cole Barrett's Reality Check
The Unvarnished Bottom Line"Forget the old movies showing floor traders screaming in trading pits. Modern financial markets live entirely inside Electronic Order Books: high-speed servers in New Jersey matching millions of orders every second. If your order isn't visible in the electronic book, you're sitting in an off-exchange dark pool, waiting to see what price the market makers decide to give you."
Interactive Simulator: Test the Math
Real-World Example: Scenario Breakdown
Examining the real numbers for: Execution of a 2,000-share purchase on an exchange with an electronic limit book showing 500 shares offered at $50.00 and 1,500 shares at $50.05
| Execution Metric | Direct Electronic Book Routing | Payment for Order Flow Retail Route |
|---|---|---|
| Fee / Rate | $0.003/share direct routing cost | $0 advertised commission |
| Spread / Buffer | Submitted a sweep order directly into the exchange's electronic matching engine | Order intercepted before reaching the exchange and held at an internalizer desk |
| Execution / Status | Matched instantly: 500 shares cleared at $50.00, remaining 1,500 shares swept at $50.05 | Filled all 2,000 shares at the flat offer of $50.05; zero price improvement passed through |
| Total Cost / Result | Transparent execution directly through the central matching engine | Missed lower-priced liquidity resting on the public book |
How Brokers Weaponize This Term
Use Level 2 or Level 3 Depth of Book feeds to see real-time order depth on the Electronic Order Book. Looking at the size of resting limit orders helps you avoid submitting large market orders that could sweep through multiple price levels and trigger severe slippage.
Broker Evaluation Matrix
Cole Approves
Interactive Brokers: Provides institutional access to deep Electronic Order Book feeds (Nasdaq TotalView, NYSE OpenBook) across all major global exchanges.
Read Audit →Cole Flags / Avoids
Gamified Mobile Apps: Hides detailed order book depth from retail interfaces, keeping users unaware of market depth and spread conditions.
View Trap Details →Frequently Asked Questions
What is the difference between top-of-book and depth-of-book?
Top-of-book shows only the single best prevailing bid and ask price (Level 1). Depth-of-book shows all resting limit orders stacked at prices above and below the current market (Level 2 and Level 3).
Can my limit order be skipped in the electronic order book?
Under strict price-time priority, your order cannot be skipped by an order at a worse or identical price placed after yours, unless a hidden or iceberg order holds higher queue priority.